Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L97/00—Compositions of lignin-containing materials
  • C08L97/02—Lignocellulosic material, e.g. wood, straw or bagasse
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N1/00—Pretreatment of moulding material
  • B27N1/006—Pretreatment of moulding material for increasing resistance to swelling by humidity
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/20—Carboxylic acid amides
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
  • C08L2666/14—Macromolecular compounds according to C08L59/00 - C08L87/00; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L61/00—Compositions of condensation polymers of aldehydes or ketones; Compositions of derivatives of such polymers
  • C08L61/20—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen

Definitions

• This invention relates to an improved method for preparing wood composition board, such as hardboard, fabricated consolidating fibers or chips under heat and pressure to form an integral board material.
• the method incorporates applying an aqueous polymeric composition, also known as a prepress sealer, to the surface of a fibrous mat prior to subjecting the mat to a high temperature and pressure press treatment.
• Wood composition board such as, for example, hardboard is manufactured by the reconsolidation of defiberated wood chips under heat (up to about 450 F.) and pressure (up to about 1000 p.s.i.).
• the fibrous particles are first formed into a unitary mat (either by a dry process, wet process, or wet-dry process) which is then consolidated into a solid board by applying heat and pressure.
• compositions containing aqueous polymeric dispersions, aminoplast resins, phenol-formaldehyde resins, waxes and the like may be applied to the mat to increase strength, improve surface integrity, and enhance water resistance. These compositions are referred to as "prepress sealers".
• Great Britain Patent 1,484,053 discloses impregnating a paper carrier web with an aqueous solution of an aminoplast resin, and drying the impregnated web in such a way that it contains 40 to 60% by weight of aminoplast resin precondensate, relative to the weight of the paper; and coating the dried impregnated web with an aqueous dispersion comprising a curable resin composition which is a mixture of A) a hard and brittle copolymer which has been obtained by copolymerization of certain monomers, and B) a rubbery-elastic copolymer which has a glass transition temperature not higher than +10 C., and has been obtained by the copolymerization of certain monomers, including 0 to 2% by weight of a crosslinking monomer with at least two reactive non-conjugated double bonds in the molecule. Further disclosed is coating the impregnated paper web and pressing the resulting film onto a pressboard sheet. This reference does not disclose the application of a polymer dispersion/amino
• U.S. Pat. No. 4,201,802 discloses a process for manufacturing prefinished hardboard which includes the use of an aqueous pre-press sealer containing a polyvinyl alcohol polymer together with emulsified fatty acids or esters, a volatile amine, and aluminum, zinc, or calcium stearates as well as driers or catalysts if desired.
• the polyvinyl alcohol is disclosed to be preferably "a homopolymer of vinyl alcohol monomer copolymerized to provide a polymer although a copolymer can be used containing very minor amounts up to about 5% of other ethylenically unsaturated monomers containing carbon-to-carbon double bond unsaturation.”
• the polyvinyl alcohol is described as partially hydrolyzed, preferably 85 to 90% hydrolyzed. This reference does not teach or suggest the importance of the gel content of the dispersed polymer.
• U.S. Pat. No. 4,238,438 discloses a pre-press hardboard treatment comprising applying to the surface fibers of a fibrous mat from 8 to 30 grams per square foot of a coating of a surface consolidating agent comprising from 50 to 95% water, from 4 to 25% of a hydroxy-radical-containing compound having a boiling point between about 212 F. and 600 F. which is selected from the group of alcohols and their esters, and from 1 to 25% polyvinyl acetate, wherein the percentage of coating ingredients are based on the weight of the coating.
• the polyvinyl acetate latex emulsions disclosed are commercial materials. The reference is silent with regard to specific compositions or gel content of the polyvinyl acetate latex.
• U.S. Pat. No. 4,336,174 and U.S. Pat. No. 4,374,899 disclose a pre-press hardboard treating composition and an improved hardboard sheet produced by the coating of the wet felt mats or laps or sheets, before consolidation and drying, with an aqueous sealer composition that consists essentially of (a) blend of water-soluble melamine-formaldehyde copolymer, (b) a styrene-acrylic copolymer emulsion, (c) a small amount of an amine capable of adjusting the pH of the resulting emulsion, and (d) a crosslinking acid catalyst capable of cross-linking the composition.
• aqueous sealer composition that consists essentially of (a) blend of water-soluble melamine-formaldehyde copolymer, (b) a styrene-acrylic copolymer emulsion, (c) a small amount of an amine capable of adjusting the pH of the resulting
• U.S. Pat. No. 4,517,228 discloses a conventional process for preparing composition board products which employs a unique step of applying to a composition mat of a density of less than 60 lbs. per cubic foot prior to the application of heat and pressure, a coating composition comprising an hydroxyl or carboxylic acid-containing acrylic vehicle, a high melting wax, a melamine-based crosslinker for the vehicle, and a platelet form of talc.
• the hydroxyl or carboxylic acid acrylic vehicle is not disclosed to contain any gel content.
• U.S. Pat. No. 4,517,240 discloses a one-step process for simultaneously compressing and tempering a fiberboard panel, which includes the step of applying to the panel prior to compression thereof an effective amount of an aqueous treating composition which contains about 3-20% by weight of an acrylic or vinyl acetate emulsion polymer or solution polymer and about 0.05 to 3.0% by weight of a fluid, water-soluble organosilicone copolymer of dimethylpolysiloxane and a polyoxyalkylene ether wherein the alkylene moiety is ethylene or propylene or mixtures thereof, characterized in that the treating composition acts both as a platen release agent during the compression and as a tempering agent for imparting water resistance.
• an aqueous treating composition which contains about 3-20% by weight of an acrylic or vinyl acetate emulsion polymer or solution polymer and about 0.05 to 3.0% by weight of a fluid, water-soluble organosilicone copolymer of dimethylpolysiloxane and
• Acrylic polymers included alkyl methacrylate/alkyl acrylate/acrylic or methacrylic acid and styrene/alkyl acrylate/N-alkylol acrylamide/acrylic or methacrylic acid copolymers, for example.
• the polymers were not disclosed to include any gel content.
• U.S. Pat. No. 4,075,141 discloses coating compositions which contain crosslinked polymeric microparticles and a carboxylic acid amide interpolymer which may be combined with an aminoplast resin crosslinking agent.
• the compositions are disclosed to be useful for application to substrates such as paper, metal, wood, paperboard, plastic, foam, extruded rubber, and the like. Neither specific gel content nor use on wood composition board are disclosed.
• U.S. Pat. No. 4,062,823 discloses compositions incorporating a mixture of at least two copolymers of acrylic monomers, a crosslinked latex, an amine, an amino resin crosslinking agent, and water or water and an organic solvent. The use of these compositions as water-based paints is disclosed. Neither specific gel content of the crosslinked latex nor use on wood composition board are disclosed.
• a prepress sealer composition is provided .
• the prepress sealer is used in the process of making wood composition board, the process is improved as a result of more facile release of the formed composition board from the press plates.
• the prepress sealer is used, the water resistance and surface toughness properties of the formed board are also improved.
• This invention is directed to an improvement in the process for manufacturing wood composition boards wherein an aqueous composition, defined herein as a "prepress sealer", is applied to a fibrous mat composed of wood fibers or chips prior to the consolidation of the mat to an integral sheet under heat and pressure.
• the prepress sealer incorporates a crosslinking resin such as, for example, an aminoplast resin and an aqueous dispersion of acrylic polymer particles wherein the acrylic polymer particles have a THF(tetrahydro-furan) gel content of greater than about 70%.
• wood composition board includes the various hardboards, fiber boards, particle boards, wafer boards, and strand boards, such as, for example, wet processed hardboards, dry processed hardboard, wet/dry processed hard boards, medium density fiber board, oriented strand board, and mende boards.
• the prepress sealer incorporates a crosslinking resin, that is, a species adapted to react with functionality incorporated in or associated with the acrylic polymer particles under the conditions attained during the manufacture of the wood composition board.
• a crosslinking resin that is, a species adapted to react with functionality incorporated in or associated with the acrylic polymer particles under the conditions attained during the manufacture of the wood composition board.
• One class of crosslinking resins suitable for use in this invention are aminoplast resins such as, for example a melamine-formaldehyde crosslinking agent, a urea- formaldehyde crosslinking agent, or mixtures thereof.
• Other crosslinking resins which may be used in the practice are multi-functional resins such as, for example, multi-functional hydroxyalkyl amides and multi-functional N-alkylol amides.
• the prepress sealer incorporates an aqueous dispersion of acrylic polymer particles wherein the acrylic polymer particles have a THF gel content of greater than about 70%.
• the aqueous dispersion of acrylic polymer particles may be prepared by any aqueous polymerization technique known in the art such as, for example, suspension polymerization and emulsion polymerization. Emulsion polymerization is preferred.
• the acrylic polymer particles have an acrylic content of at least about 20% by weight of the total weight of the polymer. Preferred is an acrylic content of at least about 40% by weight of the total weight of the polymer.
• the acrylic polymer-particles are prepared by the polymerization of ethylenically unsaturated monomers.
• the acrylic content results from the polymerization of acrylate or methacrylate esters, amides, acids, and the like, such as, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, i-butyl methacrylate, i-bornyl methacrylate, acrylamide, acrylonitrile, hydroxyethyl methacrylate, hydroxypropyl methacrylate, methylol (meth)acrylamide, methylolated ureidoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, acrylic acid, methacrylic acid, and acryloxypropionic acid.
• acrylate or methacrylate esters, amides, acids, and the like such as, for example,
• the non-acrylic portion of the acrylic polymer particles results from the polymerization of styrenics and other ethylenically unsaturated monomer such as, for example, styrene, substituted styrenes, butadiene, vinyl acetate, vinyl versatate, crotonic acid esters, maleic acid, fumaric acid, and itaconic acid.
• styrenics and other ethylenically unsaturated monomer such as, for example, styrene, substituted styrenes, butadiene, vinyl acetate, vinyl versatate, crotonic acid esters, maleic acid, fumaric acid, and itaconic acid.
• the gel content of the acrylic polymer particles may relate to crosslinking of the polymer molecules within the particles. Such crosslinking may occur during or subsequent to the preparation of the particles, or by a combination thereof. Crosslinking may be effected by the incorporation of multi-ethylenically unsaturated monomers into the polymerization.
• the multi-ethylenically unsaturated monomers may be acrylic such as, for example, 1,4-butyleneglycol dimethacrylate, trimethylolpropane triacrylate, and allyl methacrylate or non-acrylic such as, for example, diallyl phthalate and divinyl benzene.
• Gel content is preferably effected by the incorporation of allyl methacrylate into the acrylic polymer particles at a level of about 0.2% to about 5% by weight based on the weight of the polymer particles. More preferred is the incorporation of allyl methacrylate into the acrylic polymer particles at a level of about 0.3% to about 2.0% by weight based on the weight of the polymer particles.
• the glass transition temperature (Tg) of the acrylic polymer particles may be in the range of about 15 C. to about 100 C., as determined by differential scanning calorimetry. Preferred is a Tg of about 20 C. to about 50 C.
• the acrylic polymer particles may include blends of polymers; incorporating polymer(s) with a Tg greater than about 50 C. in blends is useful in increasing the surface hardness of the resulting board.
• the acrylic polymer particles have a THF gel content greater than about 70%.
• the THF gel content as defined herein was determined by preparing a 2% mixture of polymer particle solids in 1 ounce of tetrahydrofuran. The exact solids of the mixture was determined by drying the solution at 150 C. for a period of 30 minutes. The 2% mixture was shaken overnight and transferred to a tared centrifuge tube. The tube was spun down on an ultracentrifuge at 50,000 rpm for 2.5 hrs. The supernatant solution was decanted off, most of the THF was allowed to evaporate at room temperature, and then dried down at 150 C. for 30 minutes. Duplicate runs were carried out. The THF gel fraction was the proportion of polymer which was not dissolved in the supernatant solution.
• the prepress sealer of this invention may also be compounded with waxes, pigments, fillers, reinforcing agents, flow control agents, release agents such as, for example, calcium stearate, antifoaming agents, and the like.
• the prepress sealer may be applied to the surface of the mat by conventional techniques such as, for example, spraying.
• Samples 2-4 and Comparative Sample A The samples were prepared according to the method of Example 1 with the exception that a different monomer emulsion (ME#1) was used in each case as indicated in Table 2.1 and that the polymerization of Sample 2 was carried out in a 5 gallon reactor with a five-fold increase in the quantities of all ingredients.
• the resulting dispersions exhibited the properties tabulated in Table 2.2.
• ammonium persulfate in 150 g. DI water were begun.
• the addition of ME#1 and the ammonium persulfate solution were completed in 180 minutes and a rinse of 50 g. DI water was added.
• the temperature was at 79 C.
• 50 g. DI water was added, and cooling was initiated.
• Thirty-five minutes later with the temperature at 55 C. three solutions were added: 1.0 g. t-butyl hydroperoxide in 5.0 g. DI water; 0.6 g. sodium sulfoxylate formaldehyde in 15.0 g. DI water; and 7 g. of a 0.15% aqueous solution of ferrous sulfate heptahydrate.
• aqueous dispersion solids To 100 g. of aqueous dispersion solids was added 10 g. of aminoplast resin(CYMEL 303; 100% active) and 10 g. of Calcium Stearate(50% solids active) with stirring.
• the mixture (“prepress sealer") was diluted to 20% total solids with DI water.
• the prepress sealer was sprayed uniformly at an add-on of 10 grams per square foot onto a dry process fiber mat containing resin binder, wax, and moisture.
• the fiber mat was placed in a press with a 450 F. platten temperature and subjected to 380 p.s.i. pressure for 1 minute.
• the resultant board product had a density of about 1.05 and was about 1/8 inches thick.
• the press releasing performance was rated immediately after the completion of the press cycle, i.e., when the press pressure reached zero, using the following scale:
• the samples of this invention demonstrate superior press release.
• a Cobb unit is defined as the amount of distilled water weight increase in grams per 100 square inches of surface area per 24 hour period.
• Boards for measurement were cut into 5 inch by 5 inch squares.
• An Aluminum ring of 4 inch inside diameter, wall thickness of 3/8 inch and height of one inch was affixed to the test boards with beads of butyl caulk(which had been determined not to contribute to weight change).
• the boards with rings and control boards without rings were equilibrated for seven days at 65-75 C. and 50-60 % R.H.
• the boards with rings and the control boards were weighed.
• the ring was filled with approximately 1/2 inch of distilled water. After 24 hours the water was poured out, the ring surface was blotted dry with a soft paper towel, and the board with ring was weighed.
• the control board was then weighed; if the weight of the control board had changed by more than 0.20 g., the entire test was abandoned.
• the weight change for the board with ring was multiplied by 7.96 to yield the Cobb unit value.
• All of the prepress sealers have substantially lower water pickup than when water is used as the prepress sealer, that is, all function to render the formed board more water resistant.
• the surface integrity of wood composition boards to which a prepress sealer had been applied was evaluated by a tape adhesion test.
• a board sample approximately 4 inches by 6 inches was selected.
• a strip of tape (3M tape #610 was used) was placed on the surface of the board and pressed on the surface by rubbing it with the tape roll. One end of the tape was pulled off with a quick steady motion with the pulled end of the tape at a 90 degree angle to the tape adhering to the board. The % of fiber pull was evaluated visually.
• the samples of this invention display a higher surface integrity than the comparative sample as evidenced by lower levels of fiber pull in the surface integrity test.
• EXAMPLE 9 Prepress sealers based on aqueous copolymer dispersions incorporating different acids.
• DI water were begun. The addition of ME#1 and the persulfate solution were were complete in 180 minutes and 10 g. DI water was added. Thirty minutes later with the temperature at 84 C., cooling was initiated. Nine minutes later, with the temperature at 74.2 C., 37.2 g. of DI water was added and cooling was continued. Thirty-nine minutes later, with the temperature at 54.5 C., three solutions were added: 0.8 g. t-butyl hydroperoxide in 4 g. DI water; 0.48 g. sodium sulfoxylate formaldehyde in 12 g. DI water; and 5.6 g. of a 0.15% aqueous solution of ferrous sulfate heptahydrate.
• Sample 17 which has a gel content outside the scope of this invention exhibits very poor press release with or without crosslinking resin.
• Sample 18 of this invention exhibits poor press release without crosslinking resin, but excellent press release when formulated into a prepress sealer with a crosslinking resin.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Wood Science & Technology (AREA)
• Medicinal Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Polymers & Plastics (AREA)
• Forests & Forestry (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Sealing Material Composition (AREA)
• Laminated Bodies (AREA)
• Breeding Of Plants And Reproduction By Means Of Culturing (AREA)
• Protection Of Plants (AREA)
• Medicines Containing Plant Substances (AREA)
• Paints Or Removers (AREA)
• Food-Manufacturing Devices (AREA)
• Measurement Of Force In General (AREA)
• Measurement Of Radiation (AREA)
• Polymerisation Methods In General (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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Cited By (8)

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Citations (10)

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• 1991
  • 1991-01-14 CA CA002034130A patent/CA2034130C/en not_active Expired - Fee Related
  • 1991-01-17 CN CN91100307A patent/CN1053628A/zh active Pending
  • 1991-01-21 AT AT91300450T patent/ATE150064T1/de not_active IP Right Cessation
  • 1991-01-21 EP EP91300450A patent/EP0439314B1/en not_active Expired - Lifetime
  • 1991-01-21 DE DE69125040T patent/DE69125040T2/de not_active Expired - Fee Related
  • 1991-01-21 DK DK91300450.3T patent/DK0439314T3/da active
  • 1991-01-22 NO NO91910242A patent/NO910242L/no unknown
  • 1991-01-23 MY MYPI91000106A patent/MY105330A/en unknown
  • 1991-01-23 BR BR919100277A patent/BR9100277A/pt not_active IP Right Cessation
  • 1991-01-23 NZ NZ236863A patent/NZ236863A/en unknown
  • 1991-01-24 IE IE025591A patent/IE910255A1/en unknown
  • 1991-01-24 PT PT96572A patent/PT96572A/pt not_active Application Discontinuation
  • 1991-01-24 JP JP3007189A patent/JP2942365B2/ja not_active Expired - Fee Related
  • 1991-01-24 AU AU69961/91A patent/AU644402B2/en not_active Ceased
  • 1991-01-24 FI FI910368A patent/FI910368A/fi not_active Application Discontinuation
  • 1991-01-25 KR KR1019910001225A patent/KR910014188A/ko not_active Application Discontinuation
• 1995
  • 1995-05-02 US US08/432,649 patent/US6120717A/en not_active Expired - Lifetime

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